Polyphase plate-circuit excitation system



Oct. 11, 1927. ,645, 91

A. NYMAN ET AL POL YPHASE PLATE CIRCUIT EXCITATION SYSTEM 'Filed Aug. 180 1921 Fig I o 7 1a 4 5686 3,: *3 38 2 34 Hlli/ y 36 o 4 ea 46 E [7 g 136' ,4 r? ,5 V

WITNESSES: INVENTORS.

Fran/r Conrad .,and

BY W latented Get. 11 1927.

UNITED STATES PATENT OFFICE.

ALEXANDEB NYMAN, OF S'i/V'ISSVALE', AND FRANK CGITRAD, F SYLVANIA, ASSIGNG'RS TO EUESTINGHU'USE ELECTRIC AND PITTSBURGH, PENN- MANUFACTUR'ING COM- PANY, A CURPORATION OF PENNSYLVANIA.

POLYPHASE PLATE-CIRCUIT EXCITATION SYSTEM.

Application filed August 18, 1921.

tion for thermionic tubes wherein the ripple in the current supplied tothe tubes is re duced very materially.

' Still another object of our invention is to provide a scheme of transformer connections such that loads drawing direct-current components of energy may be supplied therefrom 0 without resulting in the saturation of the iron cores of the transformer.

A further object of our invention is to provide an oscillation-generator system wherein modulated impulses of radio-frequency energy may be successively impressed upon an antenna circuit at such intervals as to cause substantially constant currents to traverse the antenna circuit.

Other objects of our invention will be apparent from the following description, when taken in connection with the accompanying drawing and claims; a

Heretofore, one of the main diflicult-ies encountered in employing polyphase currents to energize vacuum-tube oscillators has been to obtain an arrangement of transformer connections wherein the secondary windings will be traversed by currents which alternate in direction. As may readily be seen, since the oscillator tubes drawdirectcurrent components of energ a uni-directional field will be built up producing saturation of the magnetizable members of the transformer unless some provision is made direct-current components.

l ve havefound that, by employing transformer connect-ions, as hereinafter described, the desired results may be obtained by employing only one tube per phase, whereas, heretofore, two oscillator tubes per phase have been required.

to neutralize the magnetizing effect of such.

Serial No. 493,379.

Our invention may be best understood by reference to the accompanying drawings,

wherein Fig. l is a diagrammatic View of circuits and. apparatus embodying our invention,

wherein two Scott-connected transformers are employed Fig. 2 is a similar view, but shows a trans former having a simple star-connected secondary winding with connections for six phases, and

Fig. 3 is a similar ondary winding of nected in delta.

In the embodiment of our invention shownin Fig. 1, we have shown polyphase supply conductors 6, 7 and 8 connected to the Scott connected primary windings 2 and 3 of a transformer l, which is also provided with Scott-connected secondary windings 4 and 5, the winding a being connected to the middle point of the winding 5.

A plurality of evacuated electric devices 9, l1 and 12, which, for purposes of illustration, have been shown as thermionic tubes comprising plates 13, 14 and 15,, grids 16, 17 and 18, andfilaments 19, 21 and 22, respectively, are adapted to be energized b.

View showing the s.ec-- the transformer con- 18, 14 and 15 are connected to the three-phase terminals of the Scott-connected secondary windings by means of conductors 22, 23 and? 2 1. The filaments are connected to a common point by means of conductors 25, 26 and 27 and are also connected, by means of a conductor 28, to a central point 29 in the winding 4. The conductor 28 may include a sustaining inductance 31 which serves'to reduce the ripple of the direct currentssupplied to the plate.

The filaments may be energized by any means well known to the art. In the draw ings, we have shown one means of energization wherein the filaments are heated from a common source of energy 32..

As a matter of illustration, we have shown the evacuated tubes adapted to function as oscillation generators in such manner that substantially constant oscillations are caused to traverse an antenna circuit comprising an lead 35.

y the secondary windings 4 and 5. The plates ment circuit for the vacuum tube 11 com;

lator tubes are required. each tube are connected to a common conprises a conductor 12 a conductor 48' the )ort1on38 of the 7 n 7 l 9 tuning coil as and the return lead 59. A plate-filament circuit for the vacuum tube 12 comprises a conductor 4%, a stopping condensers?) the conductor 13 the ort1on38 ofthe coupling coil 3 1 and'the return conductor 39. It will be noted that the platefilament circuits of the tubes are alike.

The grids 16, 17 and 18 have been shown as connected by conductors 16, 17 and 18, each of which includes a condenser a9 and a grid leak 51 for causing the grids to assume the proper negative potential, to such point on the tuning coil that a portion is included in the grid-filament circuit'of each tube. i i

In order to derive a threephase supply from the secondary windingse and 5, the conductor 28 is connected to the transformer winding 4; atsuch point 29 that the number of turns included in the portion 58 between said point and the free terminal is just twice that included in the portion 54 between said point and the terminal which is connected to the midpoint of the winding 5.

Referring to Fig. 2, I have shown atransformer 55 which employs a six-phase starconnected secondary winding 56. It will be noted that, 111 this arrangement, sir: oscil- The filaments of ductor 57 which is tapped to the neutral point 58 of the star connection. previous figure, the common conductor. 57

may also include a sustaining reactor 31.

The general connections. of the plate-filament and grid-filament circuits of each of the tubes are similar to those of Fig. 1.

Referringto Fig. 3, the arrangement here 1 shown differs from that of the previous figures in that a. delta-connected secondary winding 59 is employed and that the filaments are excited directly from the secondary winding, though a system ofexcitation,

of the windings 79, 7

one terminal of each filament beingv con-'- as shown in Figs. 1 and 2, is equally applicable to this system.

The plates 61, 62 and 63 0f the tubes 64c, 65 and 66 are connected by conductors 67, 68

and 69 through the windings 71, 72 and 7 3 to mid-points 7 1, 7 5 and 7 6 of the polyphase reactance device to the windings 77, 78 and 79, respectively. The filaments 81, 82 and 83 of the. tubes 6st, 65 and 66, respectively, are connected across pzort-ions 841, 85 and 86 and 7 8, respectively,

411, a stopping condenser 7 As in the nected to the delta terminal which is oppo site the mid-point to which the corresponding plate is connected. 7

A11 artificial neutral point for the delta is obtained by means of three condensers 87 opposite terminals of which are connected to the phase-terminals of the delta and to a common point 88. The plates and grids of the oscillator tubes are connected to the tuning coil 34:, as in the previous figures. The

filament return conductor 39 however, instead of being connected directly to the filaments, is connected to the artificial neutral point 88 of the delta.

It will be noted that, in this system, as in Fig. 1, it is necessary to employ only one tube per phase in order to neutralize the saturation effects of the direct-current components of energy.

In order to simplify our invention, in so far as possible, we have omitted means for controlling or modulating the energy which is to be radiated from the antenna system. As will be readily understood by those skilled in the art, however, any of the well known systems of modulation may be employed in our invention.

Referring to Fig. 1, the operation is as follows come positive in the order in which they are mentioned, direct currents are first caused to flow through the portion 53-01 the winding 4, then through portions 54 and 89 of the windings 1 and 5 and lastly through portions 5a and 91 of the windings 4 and 5. Assuming, as hereinbefore stated, that the number of turns included in portion 53 is twice that included in portion 5a and that the currents supplied to each tube are equal, it will readily be'seen that the magnetizing effect of the direct currents is completely nullified.

Assuming the constants of the plate-filament and grid-filament circuits of the oscillator tubes adjusted to the proper value,

erated by each of the tubes are modulated at frequencies corresponding to those of the impressed electromotive forces, their combined effect in the antenna system is to produce currents of substantially constant amplitude and frequency.

.Referring to Fig. 2, it will readily be seen that the magnetizing effect of the direct currents supplied to the tubes 92, 93 and 94; is neutralized by those currents which are supplied to the tubes 95, 96 and 97.

The thermionic tubes in the system shown in Fig. 2, as in the previous system, are op-.

ieratively connected to the antenna circuit and are adapted to generate radio-frequency currents during such periods as their plates have positive electromotive forces impressed thereon.

Referring to Fig. 3, it will be noted thatthe ma net-izing effects of the direct-current impulses drawn by the tubes 64, 6'5 and 66 are neutralized, by reasonof the derivation of potentials from the mid-point of one winding to the opposite delta terminal. Thus, when the mid-tap 74 is positive with respect to the opposite delta terminal, equal and opposite currents flow in the two halves of the winding 77, while currents flow in the windings 78 and 79 toward the point 74. lYhen the mid-tap 75 is positive with respect to its opposite delta terminal, the currents in the two halves of the winding 7 8 are neutralized, while currents flow'inthe windings 7'? and 79 toward the point 75.

It will be noted that the current then flowing in the winding 79 is opposite in direction to the current therein when the midtap T4 was positive. When the mid-tap 7 6 is positive with respect to its opposite delta terminal, the currents in the two halves of the winding 79 are neutralized, while currents flow in the windings 77 and 78 in a direction opposite to the flow when the points '75 and 74, respectively, were positive. Thus, no leg of the transformer carries currents always in the same direction, and hence there is no tendency toward saturation. 7

ll hile we have shown three embodiment-s of our invention for the purpose of illustrating and explaining the same, various modifications and adaptations will readily occur to those skilled in the art. We desire, therefore, that only such limitations shall be imposed upon our invention as are indicated in the appended claims.

lVe claim as our invention:

1. In a wireless transmission system, a polyphase source of energy, a. transformer having primary and secondary windings, the number of said primary windings corresponding to the number of phases and each primary winding being energized by the corresponding phase or" said source of energy, magnetizable cores for said windings, said secondary windings having pairs of circuit terminals, each pair constituting one phase of a polyphase source of energy, a plurality of thermionic devices, conductors for connecting individual devices to inclividual phases, one of said conductors being common to said devices and including means for maintaining substantially constant currents therein, said pairs of circuit terminals including such portions of the secondary windings as are necessary to cause the magnetizin effects of the currents in each wind ing to be nullified, means including a radiating system associated with said thermionic devices, andmeans for causing each thermionic device to function as an oscillation generator and to supply energy to said radiating system. a

' 2; In an electrical system, a source of polyphase energy, a transformer having primar and secondary windings, said primary winc ings being associated with said source of energy, said secondary windings having a Scott-connection, whereby polyphase currents may be drawn therefrom, magnetizable core members for said windings, a plurality ofevacuated electric devices drawing direct-current components of energy, there being one dev'ce for each phase, said devices having controlling electrodes and outputelectrodes, a conductor for connecting corresponding output electrodes to a central point in the secondary windings, and conductors for connecting the remaining output electrodes to the terminals of the Scott-connected windings, said central point being so disposed as to cause the magnetic effects of the direct-current components of energy to be nullified.

3. In an electrical system, a source of polyphase energy, a transformer having primary and secondary windings, said primary windings being associated with said source of energy, said secondary windings being connected in a Scott-connection, whereby polyphase currents may be drawn from the terminals thereof, magnetizable core members for said windings, a plurality of evacuated electric devices drawing direct-current components of energy, there being one device for each phase of the Scott connection, said devices having controlling electrodes andoutput electrodes, a conductor for connecting corresponding output electrodes to a central point in the secondary winding, said conductor including a reactance element tending to sustain the currents therein, and conductors for connecting the remaining output electrodes to the terminals of the Scott-connected windings, said central point being so disposed as to cause the magnetic effects of the direct-current components of energy to be nullified.

4. In an electrical system, a source of energy, a Scott-connected transformer operatively associated therewith, a plurality of evacuated electric devices drawing directcurrent components of energy, said devices comprising input and output electrodes, a conductor for connecting corresponding output electrodes to a central point in the secondary windings, said conductor including a sustaining inductor, conductors for connecting the remaining output electrodes to the terminals of the Scott-connected windings, said central point being so disposed as to cause the magnetic effects of the directcurrent components of energy to be nullified, and means including capacitance and inductance elements associated withsaid input andoutput electrodes, whereby said devices qhaviiig two windings, one of said windings being connected to A the mid-point of the other to form a threeephase Scott connection, said first-mentionedwinding being provided with an intermediate tap providing a neutral terminal, and a plurality of similar translating devices carrying unidirectional currents, the terminals of said translating devices having a common polarity being connected to said neutral terminahand the remaining terminals of said translating devices being connected to the respective three phase terminals of said Scott connection.

6; The combination with a transformer;

having Scott-connected secondary windings, of .three direct-current translating devices connected to the respective secondary phases, the-number ofturns ofa secondary included between the said connections in each phase respectively being such that the direct-current fluxes ineach Winding are neutralized.

"7. The combination with a three-phase transformer having the end of at least one winding'connected from one vphase to another, said windinghaving a Inidtap, and one or more windings providing the third phase of said transformer, of means for providing a neutral terminal, and three unidirectional-current translating devices having their terminalsof a common polarity connected to said-neutral terminal, and their remaining terminalsconnected to said windings in such manner that equalcomponents of current flow in opposite directions in the two halves of said winding having a midtap and the unidirectional magnetic fluxes in all of the windings are neutralized.

In testimony whereof, we have hereunto subscribed our names this first day of August, 1921. v

. i ALEXANDER NYMAN.

FRANK CONRAD. 

